1. Field of the Invention
The present invention relates to systems for inspecting conduits, such as underground sewer pipes, and more particularily to a new and improved conduit inspection sled.
2. Description of the Prior Art
It is common practice today to utilize television or photo-strip cameras or the like for inspecting the interior of various conduits, such as underground sewer lines, in order to determine the condition of the conduit, and thereby arrange for prompt repair, such as the closing of breaks or leaks. In a typical installation, a TV camera is mounted on a sled, preferably with the axis of the camera alined substantially coincident with the central longitudinal axis of the conduit for accuracy of observation, with a minimum of distortion. The sled is transported by cables between two open surface locations in the line or pipe, such as manholes, and the camera is connected via closed circuit to a monitor at the surface for instantaneous observation of the condition of the conduit section being traversed. As a matter of fact, the inspection sled may be a component of a train incorporating repair equipment located at a predetermined distance from the camera lens, so that upon proper positioning of the repair equipment, as observed by one viewing the monitor on the surface, the equipment can be actuated by remote control, in order to complete necessary repairs.
However, both the considerable range of interior sizes of such conduits, and the presence therein of various obstructions, such as broken pieces of pipes and inwardly projecting roots and/or laterals, present substantial problems to be overcome in efficiently and effectively carrying out such inspection. Usually, the camera carrying sleds are pre-adjusted at the surface to the interior size of the particular pipe to be inspected. A typical, present day example of such conduit inspection sleds is that produced and sold by Cues Inc. of Orlando, Fla. and Sacramento, Calif. under the designation "Q-TV Camera". This sled includes a single circular collar or band for carrying an elongated camera body and provided with a series of outstanding radial flanges on which are mounted three elongated skids on the upper side of the collar and two elongated runners on the under side of the collar, with cables being attached to the front and rear ends of the runners for transport fore and aft through the pipe.
As long as the pipe size remains constant and there are no obstructions therein, this device works well. However, when the pipe I.D. changes, e.g. reduces, and/or obstructions are met, such prior art sled must be backed out of the conduit and readjusted at the surface to conform to the smaller pipe size and/or to pass the obstructions. This requires removal of the flanges, skids and runners and replacement by another set of flanges in order to produce the reduced sled size required for continuing the already interrupted inspection operation. As will be evident, such removal, readjustment and replacement of the inspection sled is not only time consuming and tedious, but also inefficient and ineffective for accomplishing the desired objective of substantially continuous and accurate conduit inspection.
The same is true of the camera carrying and diametrically adjustable, sewer inspection sled disclosed in Tartabini et al., U.S. Pat. No. 3,794,340. For such adjustment, this patented device requires removal of a locking rod and both removal and replacement of pivot pins in a number of longitudinally spaced holes in the runner supporting frame members for varying the effective length of the linkage assembly.
Geskey, U.S. Pat. No. 1,498,446 discloses a sewer cleaning sled which also is diametrically adjustable, but only by removing and replacing both the annular cutter and the radial arms supporting the skids or runners. Vertut, U.S. Pat. No. 4,244,296, on the other hand, discloses a self-propelled, camera carrying vehicle especially designed for inspection of pipes within a nuclear installation in a radioactive atmosphere. As illustrated in the patent, the vehicle includes at least one, electric motor driven propelling wheel, and at least one pair of telescopic arms, each arm being pivoted into contact with the interior pipe wall by a torque transmitting device said to be a rotary jack (not shown) for the embodiments of FIGS. 3a and 3b, or an electric motor for the embodiment of FIG. 3c, or a spring (not shown) for the embodiment of FIG. 4. While this patented device is automatically adjustable within a pipe, it is not really a sled at all, but rather a substantially more complex, sophisticated and expensive, self-propelled vehicle especially adapted for use under the extremely hazardous radioactive conditions encountered when inspecting nuclear installation conduits. Accordingly, it would not be as feasible, as a practical matter, to utilize such a prohibitively expensive apparatus for ordinary conduit inspection purposes.
Likewise of interest is the drive unit, for otherwise unspecified internal pipe line equipment, as taught by Rhoden, U.S. Pat. No. 4,177,734. However, this patent also is directed to a self-propelled vehicle, wherein the hydraulic or pneumatic drive motor is mounted parallel to the pipe axis instead of transversely thereof, in order to permit the unit to operate in smaller diameter pipes. While this device also is diametrically adjustable, this is accomplished by a reciprocal fluid motor and toggle assembly supporting a wheel, with the extent of such adjustment being limited for facilitating entry of the vehicle into a pipe.
While the following patents are of interest because they disclose various usages of sled type transporting device generally, the same are not analogous to the inventive field of conduit inspection. Kirk, U.S. Pat. No. 2,299,993, merely discloses a ski stretcher with collapsible legs. Robinson, U.S. Pat. No. 2,394,264 teaches a combined stretcher and fracture board on skids. Murray, U.S. Pat. No. 2,725,239 discloses a combined toboggan and sled type mobile container with retractible and extensible runners movable by manual operation of a lever and linkage. Finally, Cawl, U.S. Pat. No. 2,612,380 is merely directed to a vacuum cleaner runner assembly.
Another problem occurs when the sled runs into a blank wall during conduit inspection and can not be pulled through the outlet manhole. It then becomes necessary to reverse the direction of sled movement by pulling on the previously slack rear cable and leaving the front cable slack. The difficulty here is that if the sled already has passed by an obstruction, it may not be able to do so in the reverse direction for a number of reasons, such as the angle at which the obstruction projects or change in orientation of the sled. None of the prior art devices referred to above is seen to offer a simple and effective solution to this problem either.